Dynamic mechanical response and deformation mechanisms of Al ₁₈ Co ₁₈ Cr ₁₄ Fe ₁₄ Ni ₃₆ eutectic high‐entropy alloy with multi‐ heterogeneous microstructure

Abstract Eutectic high‐entropy alloys (EHEAs) exhibit excellent as‐cast mechanical properties resulting from intrinsically distinctive microstructures. As a representative class of heterostructured metallic materials, however, research regarding the dynamic tensile behavior of heterostructured EHEAs remains scarce at present. In this work, we investigated the correspondence between deformation mechanisms and mechanical performances of Al 18 Co 18 Cr 14 Fe 14 Ni 36 EHEAs with lamellar regions and non‐lamellar regions under quasi‐static and dynamic tensions. The tensile results showed that the strength and ductility of the EHEA exhibits a progressively sequential improvement with the increasing strain rates, which display a remarkably synergistic enhancement as the strain rate reaches 4200 s −1 . The lamellar regions can facilitate forming the continuous dislocation slip and transmission within the dual‐phase lamellae under varying strain rates, leading to synergically deforming, in contrast with non‐lamellar eutectic regions due to cellular B2 particles hindrance to dislocation motion. The remarkable enhancement of mechanical properties with increasing the strain rate is related to plastic deformation mechanism transformation from single dislocation slip dominated by stacking faults to the activation of twinning deformation. Furthermore, severe hetero‐deformation induces additionally back stress strengthening accompanied by the activation of geometrically necessary dislocations in hetero‐zones. Our investigation on the dynamic behavior of the EHEA can help understand the relationship between micro‐mechanisms and mechanical performances to architect optimal microstructure design for engineering applications.